In construction of buildings or the like, beams are used to span between upstanding members which may be columns. The beams are adapted to carry loads such as a concrete floor. It has been known to use both steel and concrete as beams. Steel is often used because of its enhanced to load bearing characteristics per unit weight over concrete beams. Accordingly, steel beams, i.e. I-beams, are erected to span between columns and carry the designed loads. It has also been known to use external tensioning of the steel beams. External tensioning is accomplished by suitable location of the columns and by tensioning the beam to span therebetween.
In addition to steel beams it has been known to use concrete beams which may be internally post or pre-stressed. To construct the concrete beams, a network of steel cables extends through and along the length of the beam. If the beam is to be pre-stressed, the cables are positioned in a mold, the mold having steel plates at its ends. Hydraulic jacks or the like are used to tension the cables in the mold. Thereafter concrete is poured into the mold between the end plates to encase the cable network. After the concrete has sufficiently hardened, the tension cables are secured to the end plates and released to place the concrete beam in compression. In post-stressing, the network of cables is positioned and concrete is poured thereabout either in a mold or in situ to encase the cables. End plates are attached to the concrete beam, certain cables extending therethrough. After the concrete is sufficiently hardened, the cables are tensioned and thereafter secured to the end plates and released to place the concrete beam in compression. The aforementioned pre-stressing and post-stressing techniques are effective to enhance the load bearing characteristics of the beam.
Heretofore, however, it is believed that it has been unknown to apply post-stressing techniques to enhance the load bearing characteristics of other types of beams such as steel, aluminum or others.
The beams in some if not most cases provide support for a floor in the structure. This floor may be concrete. To form the floor, it has been known to pre-cast a concrete beam according to the method described above, the beam including a portion of the floor. When the beams are set in place between the columns, the floor portions mate to define an overall concrete floor for the structure. This technique is common for parking garages or the like. However, a problem with this technique is that the seams between the four sections and between the beams and columns tend to leak, causing unslighty watermarks and other related problems. Further the structure may not be able to withstand a seismic event of any significant intensity.
Further it is believed that this construction technique of pre-casting or assembling the beam and floor portions is time consuming and costly.
Another method to form a concrete floor is to erect forms to receive liquid concrete for forming, in situ, the floor and some or perhaps all of the concrete beams. To hold the concrete until it hardens, these forms are supported by a network of shoring assembled beneath and bearing the loads of the forms and liquid concrete. These forms are constructed and supported so as to encase any structural steel or the like within the concrete. As can be appreciated, the network of shoring and the construction of the forms is time consuming and costly. The present invention is directed toward to overcoming the problems noted above.